If you’re missing dead-simple FileDownloader-like capabilities in plain Java Flow, this add-on is for you: https://vaadin.com/directory/component/file-download-wrapper
You can either use it to create a download text link or wrap a component like Button to start a download. There are multiple possibilities for providing the downloadable data: you can give it a File object, a StreamResource or use the DownloadBytesProvider interface. Check the add-on page and the [demo]
(https://github.com/OlliTietavainenVaadin/file-download-wrapper/tree/master/src/test/java/org/vaadin/olli) for usage examples. Issues can be reported to the [GitHub tracker]
(https://github.com/OlliTietavainenVaadin/file-download-wrapper/issues).